Breech mechanism for guns having replaceable liner



| MACKTA 2,618,877

BREECH MECHANISM FOR GUNS HAVING REPLACEABLE LINER NQV. 25, 1952 5 Sheets-Sheet 1 Original Filed May 7, 1945 awe/Mm NOV. 25, 1952 MACK-[A 2,618,877

- BREECH MECHANISM FOR GUNS HAVING REPLACEABLE LINER Original Filed May 7, 1945 3 Sheets-Sheet 2 a Ln Mack-1a L. MACKTA Nov. 25, 1952 BREEICH MECHANISM FOR GUNS HAVING REPLACEABLE LINER 3 Sheets-Sheet 3 Original Filed May '7, 1945 an Mackfa Patented Nov; 25, 1952 BREECH 'IVEE'CHANISM FORCwHJ'NS'HAVING? REPIiACEABLE-LINERi Leo Mackta, Brooklyn, N. Y.

Original application May 7", 19 5, Serial No: 592,435: Divided and this applicatiomJanuary 26 19501Sli3lN0'. 140,702

13. Claims.-.

(CLAZe-l) (Granted under" theact of"March 3, 1883; as amended AprilL30, 1928; 3 70 0..G. 757)-- The invention described herein maybe-manu= factured' 'and used "by 'orfor the G'overnmenhfor" governmental "purposes, without thepayment to m of'fany royalty thereon:

This'applicati'on'is a divisionof mycopending-r application; SerialNumber' 592335; filed" May '7'; 1945; now Patent2,549,832' dated Aprilt2-4; 1951';

It is the main" obj ect' ofthe invention to pro vide' a" novel breach structure forguns of particular-value'where a separable and readily-re= placea'bleirifl'ed'lineris used'ina generally smoothboreibarrel.

Another'obj ect' is 'to*provide a breech" structureof*particu'la1" value iniconnection with" ammunition wherein; each. round consists" of a unit--- in eluding 'a cartridge'enclosedwithinia rifledliner; the-structure being so constructed and arranged as to enable'axial translation: of'the: liner forwardly into operativepositionwithin the" guntubeor barrel, whilepositively-retaining the cartridge in the'breeclr chamber in firing relation' with th firing-mechanism.

Otherobjects' and" advantages will become-apparent aftera studyof the following-,dscriptiom irr connection with the accompanying drawing"- wherein Fig: 1 is alongitudinal sectional view of a" gunembodying the invention and showinga" round inposition with --its li-ner-ready to be forced for wardly into the barrel by: the retracted breech r sleeve-or liner:

Fig: 2 is-.a viewcorresponding to Fig; l show ing the'repla'ceable rifled liner rammed forwardly: into th guntube by the'operatively positionedc.

breech sleeve:- and clamped: in. position. byfthe- 35 sleeve;

Fig. 3. is arear elevation of Ithelgun withzbreeclt; open- Fig. .4. is. a;. vievw corresponding to; Fig. 3 3 but; showing the -.breech: closed.

Fig. 5. is a fragmentary; longitudinal section on: theline- 5-5 of Fig. 3,1witharound. Ofammunition chambered and the-breech sleeve zandiits .-.ob;- turatorpiston. at an intermediate .positionin opening movement toshow. initialaction of .the. 45

Fig: 8 is a fragmentary "section corresponding" 5 2;." tdFi'g: 7' but showing the firing pin in'cockedf position;

Fig. 9 is a fragmentary. longitudinal section'of" the' rear portion -of' the:,breech-;chamber; .forward i portionof th breech sleeve; obturator' piston and I means-releasablyconnecting a; cartridgeto. the piston.-

Fig. 9A=is a detail sectional view'to*an' enlarged scale ofa=-portio1r-of Fig: 9;

Fig: 10 is a longitudinal section of -the:breecli: meehanismequipped: with a" diflerentrmeans for. releasably connecting the'cartridge'zand piston:

Fig.' 11 is a section-taken in: a "planeindi'cated' by-theline-l 1 Fig; 10;

Fig: 12 is" a detail sectionali view taken in; a:

Fig. 13-'is a detail view showing toan enlarged; scale thetwo-part cocking lever *and a'- coacting portion ofthe firing-pin.

Referring indetail to -the-drawingr a" base: 1" hasa-barrel 2;=rigid1y attachedthereto; Base I may be carried-uponanyknown' mountinot' shown, f or moving the guirin' train-and elevation. The-barrel has a forward portion forming a'bore:

I 3 and a rear portion forming-- a-breech chamber:

4. The-chamber4-is of greater diameterfthan bore 3 thereby forming ashoulder 5 =at=thej Unc tion between the-two; Interrupted threads 6 "are? formedin the-rear portion of the walls' of ch-ame ber 4.? Bore which is shown with" a: forward} taper; may have a smooth" surface or; alterna tively. have its surface indented" with" smallgrooves" or recesses to increase" the -friction" beetween itself and the contactingsurface-offthe replaceable liner; to be-described later;

A breech sleeve 1 has -'a smooth sliding fit within theibreech" chamber 4; The sleeve is formedi; with an open forward end and *a- -rear endclosed. by -'ahead 8- which maybe" integral with. the. sleeve: The sleeve is--provided-with-interrupted; threads 9' on its -rear-external walls 'fortcoaction; with threads to-lock-sleeve l :withinzchamber. 4 when the partsare in the position shown at t Fig. 2;

Base l has-bearings Ill-*andlrattachedtheree to in spaced 'alignedrelation; ALrQdOrtube I2? is journaled inthese-bearingsatitsforwardfpor tion and is held against axial'movementin'the. bearings by collars-such as" Hand. 14', Figs: 1, and 2. At its'rear end; tube l2'has" an arm; l5':' fixed thereon; As" seeniii-Fig: 3'; the" arm. is rotatable clockwise with tube I2, movementibeing. limited by engagement of walug IS" with theptop surface-of base I-.-

This rod passes forwardly through a central aperture in head 8 and, at its forward end has a piston l8 fixed thereto. The piston has a smooth sliding fit within sleeve 1 and, as clearly shown upon Figs. 1 and 2, the parts are so dimensioned that piston [8' lies substantially in the plane of the rear end of chamber 4. Furthermore, when sleeve 1 is in fully retracted position as in Fig. 1. its forward end just clears the rear end of breech chamber 4 and its rear end is contiguous to arm 15, while, when the sleeve is in fully advanced position as in Fig. 2, its forward end is closely adjacent shoulder 5 and its rear end is contiguous to piston [8. The sleeve has a radially extending operating handle I9 fixed to its rear end. When fully retracted, a reduced portion of this handle fits a forked lug l5a on the upper end of arm l5 as will be clear from inspection of Figs. 1 and 10. By this construction, when the parts are in the position shown in Fig. 1, sleeve 1 and arm l5 may be rotated as a unit to the position shown in Fig. 3 to thereby fully open the breech for loading.

Tube l2 has a longitudinally-extending slot 12a through the rear half of its length. The slot faces upwardly as the parts are shown in Figs. 1 and 2. A liner ejector includes a straight rod 28 slidable Within tube l2, and a bent end 20a projecting upwardly through slot 12a and secured to the head 8 of breech sleeve 1 for movement as a unit therewith. The forward end of rod 20 is attached to a downwardly-bent arm 2 la of an ejector rod 2|. The rear end of rod 2| is turned upwardly to form an ejector portion 2) positioned to ride in and along a longitudinally-extending slot through the bottom of the portion of the barrel wall forming chamber 4. As shown in Fig. 2, the portion 2Ib lies in a radial passageway in the barrel and forwardly of and in contact with the rim of barrel liner 22 so that, when rod 20 is moved rearwardly with sleeve! portion 2lb forces the liner rearwardly therewith out of the barrel.

Piston I8 has a rearwardly-opening recess 23 for the accommodation of firing mechanism shown in Figs. 7 and 8, wherein it will be noted that rod I1 is hollow and in communication with recess 23. A firing pin 24 is slidably mounted in a central aperture inpiston l8 and extends rearwardly into a counterbore in the end of rod ll. The pin is urged forwardly to the firing position of Fig. 7 by a coil spring 25 acting between an abutment 26 on pin 24 and the shoulder formed by the counterbore in rod IT. The pin is fixed against rotation by means not shown.

The firing pin is held in the cocked position of Fig. 8 by a sear 21 pivoted in recess 23 and urged into operative position by a spring 28. When the firing pin is retracted to cocked position by mechanism subsequently described, sear 21 is first cammed downwardly by a latch 24a and then snaps upwardly into the position shown at Fig. 8'as the latch moves rearwardly, to hold the pin in cocked position. Clockwise movement of sear 2'! to release pin 24 and permit firing movement of the pin under the urge of spring 25, is effected by a cable 29 attached at one end to the scar and guided by suitably-positioned pulleys 30 to the inside of rod H. The cable extends through rod l1 and at its rear end is attached to a'ring 3|, Figs. 1, 2, and 10, whereby the cable may be pulled to manually fire the gun as by means of a lanyard.

The firing pin is automatically retracted to cocked position in response to forward translation of sleeve! into battery position, by alever 32 4 pivoted in recess 23 on an axis at right angles to the firing pin and urged into clockwise rotation as viewed in Figs. 7 and 8, by a light spring 33. Suitable stop means, not shown are provided to limit clockwise movement of the lever to substantially the position shown at Fig. 7. As shown in detail in Fig. 13, the lower end 32a of lever 32 is pivoted at 3212 to the main portion of the lever. Stops 320 on the interpivoted portions engage and prevent further clockwise movement of end 32a when this portion is in the full-line position of Fig. 13. A light leaf spring 34 secured at one end to lever 32, engages pivoted end 32a and urges it into the full-line position shown.

From Fig. '7 it is noted that the upper curved end of lever 32 projects rearwardly from the rear face of'piston I8 so that, when breech sleeve 1 is moved forwardly into battery position its head 8 engages. lever 32 and rotates the same counterclockwise. In response to this movement, end 32a engages abutment or collar 26 and forces the firing pin into cocked position at the same time compressing spring 25. A little before sleeve I reaches the position of Fig. 8, sear 21 snaps in front of latch 24a to hold the firing pin in cocked position and nose or end 32a then clears abutment 23 as the sleeve 1 moves into its limiting forward or battery position as shown in Fig. 8. The firing pin is then free to move forward under urge of spring 25 when released by a pull on cable 29 and, when sleeve 1 is again retracted, cocking lever 32 can rotate clockwise under the action of its spring 33. During this rotation pivoted end 32a engages abutment 26 and pivots against the action of spring 34, as

indicated in dotted lines in Fig. 13, until, on continuedclockwise movement of lever 32, end 32a is free to again move into the full-line, operative position of Figs. 7 and 13.

The cartridge and its enclosing barrel liner j form a loading unit which may be packaged and loaded together. The cartridge may consist of a shell or casing 35 having a specially formed head. This head may be formed with a' concentric annular channel 36. A ring 3'! is secured to the rear face of the shell and has a width 1 sufficient to form an inward flange as indicated at 38, Figs. 9 and 9A. If desired, a frusto-conical metal ring 39 may be fixed concentrically on the central portion of the cartridge head, to provide a cam surface Within the groove 36, as clearly extend forwardly therefrom in parallel helical 1 paths and when forced forwardly to the position of Fig. 2, form rifling lands snugly fitting the barrel. Since the cartridge and liner are fully disclosed and claimed in my original application above identified, no further description of this feature is deemed necessary. Sufiice it to say that when sleeve 1 is forced forward to battery position, liner 22 is engaged thereby and forced from the cartridge into the position shown at. Fig. 2, where its rim or fiange 22b is firmly:

gripped between shoulder 5 and the rim of sleeve A projectile 42 is a 1 topprevent further. forward" movement 1 of j the.

linerywithin .the barrel.

The liner-22 fits about the cartridge and thereforewthe latter tends. to move forwardly with the.

liner. away from piston 18, when sleeve I ismoved intothe battery position of Fig. 2. To prevent this .andto. retain. the cartridge in firing. relation with: the. firing pin; in piston I8, means are. providedlto, releasably. connect the head. of the i8 whereby the;

cartridge: shell with piston cartridgeis prevented from forward movement with .liner 22' and isheld in operative. relation with .firingpin 24. One suitable means isshown. in Fig. 9, 9A, .10 and 11; The construction ofthe.

cartridgeportion of such means has been previe ously described... The. cooperating portion. car-- ried; by" piston 18* will. now be. described: A

recess 43 in piston 18 opens through .theforward.

facepthereof and has a:.cup..44 secured therein as by; threading or. pressing.- Alatch. element 45 comprises applunger 45a fitting the cup, and having a stem 4% projecting through a central aperturezinithe bottom of the cup, and button or-head45c.. A spring 46 urges the latch element in- Fig: 9A tothereby secure the cartridge to thepiston I1 and prevent it from moving forwardly with liner 22 when the latter is rammed into position by sleeve 1. It is'contemplated that the cartridge case 35 may be of combustible material and hence consumed by detonation of the explosivecontained therein. However, when it is desired to open the breech without detonation of-the cartridge, sleeve T may be unlocked and withdrawn to the position of Fig. 1. Then, as the sleeve-and piston are swung laterally about the axis of rod 12, head 450 is released from flange 38'andthen cammed into recess 43 by the surface of ring 39, as will be clear from inspection of Fig. 9A. Rings 3! and 39 may also be made of combustible-materials;

In Figs. 11 and 12, Ihave shown a modified construction for securing'the piston to the head oi the cartridge. In these figures, the head 4T of :the cartridge is formed with a-peripheral' rabbet 48; A disc 49 of substantially less diameter than the cartridge, is secured to the head centrall ythereof and overhangs the rabbet to form a flange as will be clear from Fig. 10. A

showninFig: 10. The rear arm of lever 50 projectsgrearwardly througha cam slot 53a formed in asector-shaped.plate.53v integral with a tube 54 journaled on rod l1. This tubeextends rearwardlythroughheadt and arm. l5 whereit has an offset operating handle '55 fixed thereto.

a left ,portion. of graduallydncreasing radial. dis-v As; seen in Fig. 11, the. right portion of slot 53a.is. concentric ofrod. l1, which-portion merges into.

tance'fromtheaxis.of the rod... Therearend of:- leverr50 projects through slotv 53a for all positions; of. the lever'relatively to. its pivot; A cam 56 overlies. slot 53a. and is. securedat one end, as at 56a, Fig. 11', to plate 53. As. clearlyshownupon Fig. 12, the cam has a gradually increasingdis. tance from plate .53. By the construction just .de-

scribed, when a fresh round hasv been loaded andthe sleevezandpiston have beenrotatedinto.position coaxial with. the. breech, that is, the positionshown upon Fig. 1.0,.handlez55 is,v positioned. so

that the .endof lever 50 is at the right or radially; inwardmost portionof slot 530, and, under urge; of spring. 52, lever: 55 is. in its. rearwardmost positionin which. position its. forward end .lies. within: the piston. Now, as.handle.55. is .turned:- clockwise, plate 53-and cam 56 move correspondingly. Cam 56 first engagesthe adjacentendoft lever 55 and forcesthedever forwardlyuntil its. hooked endlies within rabbet 48. Then the lower. edgeof slot 53a rotates thelever counterclocke wise; as viewed in Fig..10, until itshooked. end

engagesabout'the periphery of disc-49 tothereby. lock the piston to the cartridge so that the late ter is held against axial movement when the sleeve andliner are thrust forwardly.

Inorder to eject the. liner. 22 after loading but before being rammed, means are provided as. shown-in Figs. 5 and 6, operated in response to transverse pivotal movement of the breech sleevev from the position of Fig.4 to that shownat Fig. .3. To effect this function, the. rear-end of barrellZ carries ahousing 2a (seeFigs; 3 to.6)., within which an ejector lever-51 is pivoted on a pivot 53 atright angles to thebore axisrof the gun. The free end of th lever is adapted to project through a slot in the barrel wall when pivoted counter clockwise from the position shown in dotted lines, Fig. 5', to the full line ejecting position of Fig. 6. The end of the lever is shaped to engage the rim 220 of a liner and to force the same rearwardly out of fully seated position as will be clear from inspection of Figs. 5 and 6. A second lever 59 is pivoted on pivot 58 closely adjacent lever 57'. The two levers 5? and 5% are connected by a coil spring and are so angular-1y related and positioned that when sleeve '1 is in theposition shown in Fig. 1, ejector lever 51 is in the dotted line position of Fig. 5 and lever 59 is displaced a little clockwise from its position shown in Fig. 5 wherein its end 59a projects into the path of the sleeve as the latter is swung to open position. Thus as the sleeve is swung to the open position of Fig. 3, the lever 55 is pivoted and, through spring 69, pivots lever 57 to cause nose portion 57a of the latter to engage the rim 22c and force the liner rearwardly either to forciblythrowit clear of the gun or to enable it to be manually withdrawn.

In operation, with the breech sleeve and related parts in the position shown in Fig. 3, a cartridge and liner unit is loaded into the breech chamber as seen in Fig. 1. The sleeve and its piston are then rotated into the ramming position of Fig. 1.

In the modification of Fig. 9, this movement automatically secures the cartridge to the piston to insure that the firing pin carried by the piston is in detonating relation with the cartridge and also to prevent forward movement of the cartridge with the liner.

Sleeve i is next forced into the breech chamber, moving the liner ahead of it into the bore. The sleeve is now given a fraction. of a turn to engagetheinterrupted threads 6.and.9 andlock the sleeve in battery position. As the sleeve moves into final position, its closed end engages cocking lever 32 and pivots the same to move the firing pin to cocked position, as previously fully explained. Firing may now be effected by a pull on ring 3|.

After firing, the sleeve 1 is unlocked and withdrawn to the position of Fig. 1 after which the sleeve and piston are rotated as a unit about the axis of shaft 12, to the open position 'of Fig. 3. This movement, in the species of Fig. 9, automatically disconnects the piston from the cartridge head, Of course, such disconnection may not be necessary in case the-cartridge casing is made of combustible material and is entirely consumed in the detonation of the contained explosive charge. As sleeve 1 is withdrawn, rod 21 is translated rearwardly to force the liner 22 to the position shown at Fig. 1. As the sleeve and piston unit are swung about the axis of shaft I2, the sleeve engages lever 59 as seen in Fig. 5, and pivots lever 51 either to eject the liner or to force it rearwardly so that it can be easily manually extracted.

When the cartridge lock of Figs. to 12 is employed, preferably as soon as the sleeve 'i has been turned to the ramming or retracted position of Fig. 10, handle 55 is turned clockwise to first thrust lever 53 forwardly and then pivot it downwardly to cause its hooked end to engage over the rim of disc 49 and lock the cartridge to the piston in firing relation therewith in the manner previously described. Where the cartridge casing is not consumed during detonation, the handle 55 is operated in the reverse direction after firing and after sleeve 7 has been withdrawn but before it has been swung downwardly with arm [5, to thereby disconnect the casing from piston l8 and to withdraw the lever 53 within the piston'so that the latter is free to swing downwardly with sleeve 1 to loading position. The operation of the means for extracting the liner from the barrel into the breech chamber in response to movement of sleeve 7 from battery to retracted position, and for extracting the liner from the chamber in response to swinging of the sleeve from retracted to loading positions is the same as previously described.

While I have shown the form of the invention now preferred by me, numerous modifications and substitutions of equivalents will occur to those skilled in the art after a study of the foregoing disclosure. Hence, the disclosure is tobe taken in an illustrative rather than a limiting sense and all modifications falling within the scope of the subjoined claims are reserved.

Having now fully disclosed the invention, what I claim and desire to secure by Letters Patent is:

1. In a gun, a coaxial barrel and breech chamher, said chamber having a diameter greater than the diameter of the bore of said barrel, there being an annular, rearwardly-facing shoulder between said bore and chamber, a breech sleeve having a closed rear end and an openforward end, said sleeve being adapted to slidably fit said chamber with its forward end clamping the flanged rim of a liner against said shoulder, means mounting said sleeve for axial movement to a position clear of said chamber and for revolution about an axis external of said gun to clear the breech thereof, and means comprising a piston slidably fitting said sleeve to fire a cartridge fitting said sleeve when said sleeve is positioned forwardly within said chamber.

2.'In a gun, a barrel having a bore and a position in which the open forward end of said chamber is closely adjacent said shoulder, to a retracted position clear of said chamber, said sleeve having a closed rear end, a piston slidably fitting said sleeve, a rod fixed to said piston and extending rearwardly therefrom through an aperture in the closed rear end of said sleeve, an arm fixed to said rod at the rear end thereof, bearing means fixed with said chamber and defining an axis parallel with and offset from the bore axis of said barrel, and a shaft journaled in said bearing means and secured at its rearward end to said arm.

3. A gun as recited in claim 2, and means securing said sleeve against rotation on said rod when the sleeve is retracted to rearward position on said rod.

4. A gun as recited in claim 2, there being a Q longitudinal slot through the wall of said breech chamber, extractor means projecting through said slot, and means responsive to movement of said breech sleeve from battery position to retracted position to move said extractor means along said slot from a forward position in the plane of said shoulder to a rearward position adjacent the rear of said chamber.

5. In a gun, a barrel having a bore and breech chamber coaxial therewith, a breech sleeve closed at its rear end only and slidably fitting said chamber, means mounting said sleeve for movement from a retracted position clear of said chamber, to a battery position within said chamher and for swinging movement when in retracted position about an axis parallel with and offset from the bore axis of the gun to a loading position, a piston slidably fitting said sleeve and swingable therewith only in a plane parallel to and abutting the rear face of said chamber, firing means carried by said piston, and locking means carried by said piston to secure thereto a cartridge in said chamber, when said sleeve is in retracted position whereby said firing means may operate to fire said cartridge.

6. A gun as recited in claim 5, said last-named means being operated automatically in response to swinging of said sleeve and piston from loading to retracted positions.

'7. A gun as recited in claim 5, rod means operable manually to actuate said locking means when said sleeve and piston are in retracted position.

8. In a gun, a barrel having a bore and breech chamber coaxial therewith, said barrel being adapted to receive a removable liner by insertion through said chamber, a breech sleeve open at its forward end and slidably fitting said breech chamber for movement from a battery position in said chamber to a retracted position clear of said chamber, means locking said sleeve in battery position within said chamber, a piston slidably fitting said sleeve and limited to swinging in a transverse plane parallel to and abutting the 1 rear face of said chamber, means mounting said sleeve and piston for swinging as a unit from retracted position of said sleeve to a loading position clear of said breech chamber, means responsive to movement of said sleeve from battery to retracted positions to extract the liner from said barrel into said chamber, and means responsive to swinging of said sleeve and piston from retracted to loading positions to extract the liner from said chamber.

9. A gun as recited in claim 8, and means responsive to swinging of said sleeve and piston from loading to battery positions to lock said piston to a cartridge in said chamber.

10. A gun as recited in claim 8, and manually operable means carried by said sleeve, to lock said piston to a cartridge in said chamber when said sleeve and piston are in retracted position of said sleeve.

11. In a gun, a barrel having a bore and a breech chamber, said breech chamber being of greater diameter than said bore to form a rearwardly-facing shoulder at their meeting surfaces. a breech sleeve having a radial thickness equal to that of said shoulder and slidably fitting said chamber for translation from a battery position with its forward face adjacent said shoulder, to a retracted position clear of said chamber, a piston slidably fitting said sleeve, a rod fixed to said piston and extending rearwardly through an aperture in the closed rear end of said sleeve, means external of said sleeve mounting said rod, piston and sleeve for swinging about an axis ex ternal of said gun and parallel with the bore axis thereof, when said sleeve is in retracted position, said piston abutting the rear end of said sleeve when the latter is in battery position, a firing pin in said piston and means responsive to movement of said sleeve into battery position to cock said firing pin.

12. In a gun, a barrel having a coaxial bore and breech chamber, said chamber being of greater diameter than said bore to form a rearwardly-facing shoulder therebetween, a breech sleeve slidably fitting said chamber and having a uniform wall thickness substantially equal to the radial dimension of said shoulder, closure means to close the rear end of said sleeve, means operable to lock said sleeve in position within said chamber, and means carried by said sleeve to fire a charge therein when said sleeve is in locked position, said last-named means comprising a piston slidably fitting said sleeve, firing pin means carried by said piston, a, piston rod secured to said piston and extending rearwardly therefrom through an aperture in said closure means, and means in fixed relation with said gun and mounting said sleeve and piston for swinging about an axis parallel to and offset from the bore axis of said gun.

13. In a gun, a barrel having a coaxial bore and breech chamber, said chamber being of greater diameter than said bore to form a rearwardly-facing shoulder therebetween, a breech sleeve slidably fitting said chamber and having a uniform wall thickness substantially equal to the radial dimension of said shoulder, closure means to close the rear end of said sleeve, means operable to lock said sleeve in position within said chamber, means carried by said sleeve to fire a charge therein when said sleeve is in locked position, said last-named means comprising a piston slidably fitting said sleeve, firing pin means carried by said piston, and means mounting said piston and breech sleeve for lateral movement as a unit in planes normal to the bore axis of the gun, said piston being'movable only in a plane parallel to and abutting the rear face of said breech chamber.

LEO MACKTA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 818,177 Kolb et al Apr. 17, 1906 2,088,503 Broussard July 27, 1937 

